Spark plug bushing and shield



Jan. 12, 1937.- J. J. MAscucH SPARK PLUG BUSHING AND SHIELD Filed Nov.10, 1933 I I I a u F I. I 11 INVENTOR. J0$EPH.J. M SCUCH.

A TTORNEY Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE SPARK PLUGBUSHING AND SHIELD Joseph J. Mascuch, Newark, N. J.

Application November 10, 1933, Serial No. 69'l,382

8Claims.

bushing in the spark plug opening of a cylinder head. This isparticularly true where aluminum or other alloys are used for thecylinder heads. The purpose of the bushing is to prevent wear on thethreads of the spark plug opening. The top of the bushing is placedflush with the cylinder head and the bushing is provided with internalthreads to receive a spark plug.

It is also desirable to provide means to shield the spark plug toprevent interference with radio equipment by reason of electricalemanations from the spark plugs. This can be done by means of a cupscrewed into the cylinder head in combination with a cap for the cupprovided. with a di-electric skirt such as shown in my copendingapplication Ser. No. 481,766. Where a cap is not used trouble will beexperienced by reason of flash-overs from the exposed terminal of thespark plug to the cup, unless the cup is spaced sufficiently far fromthe plug to prevent flash-overs. To do this necessitates a large andcumbersome construction.

It is desirable to provide a structure which may be used merely as abushing or which may be used as a part of a spark plug. shield, inaddition to its use as a bushing. Therefore, one object of thisinvention is to provide a spark plug bushing having a portion extendingabove the surface of the cylinder head, which bushing may be used withor without a radio shielding cap. A further object of the invention isto provide a bushing extending above the cylinder head, but which'willprevent flash-overs from the exposed terminal of the spark plug to thebushing.

It often occurs that an engine is placed in service without radioshielding and it is subsequently desired to apply radio shieldingthereto. In order to apply a radio shield it is sometimes necessary,where a bushing is used, to use a spark plug of less than standard sizeby reason of the size of the spark plug opening. or in the alternativethe spark plug opening in the cylinder head must be re-formed to make itlarger, in order to use a standard size plug with the radio shield.Therefore, a further object of the invention is to provide a bushingwhich will permit the use of a standard size spark plug and which willpermit the subsequent application of'a radio shield without the removalof any parts and without any change in the size of either the plug orthe spark plug opening in the cylinder head. A further object of theinvention is'to provide a radio shielding cap for use with such bushing.

In aircraft engines loss of efliciency is experienced by reason ofover-heating at the spark plugs. By reason of the spark plug being inintimate thermal contact with the cylinder head, the heat in thecylinder head is concentrated at the base of the spark plug, whichresults in loss of power. If the heat of the cylinder head can beprevented from accumulating at the base of the spark plug, theover-heating of the spark plugcan be prevented to a considerable extent.Therefore, a further object of the invention is to provide a spark plugbushing which will be a good electrical conductor for the purpose ofradio shielding and which will have relatively poor heat-conductingproperties so as to impede the conduction of heat from the cylinder headto the base of the spark plug.

The invention consists of the construction, combination and arrangementof parts as herein illustrated, described, and claimed.

In the accompanying drawing, forming part hereof, is illustrated oneform of embodiment of the invention, in which drawing similar referencecharacters designate corresponding parts, and in which:

Figure 1 is a vertical section of a spark plug' bushing with the sparkplug shown in outline;

Figure 2 is a side elevation of a bushing with a shielding cap thereon,a portion of the cylinder being shown in outline;

Figure 3 is an elevation of a bushing; and Figure 4 is a verticalsection of the bushing and cap shown in Figure 2.

Referring to the drawing, A designates a usual form of cylinder headprovided with cooling fins B. The head A may be made of any desiredmaterial, but it is common to make the head of aluminum alloy. The headA is carried by the cylinder block C. The head A is provided with aspark plug opening and disposed therein is a bushing 5, having ashoulder 6 adapted to seat against the surface of the head A. Thebushing 5 has a cylindrical extension 1 formed as an integral partthereof.

The bushing 5 and the extension 1 may be made of nichrome, so as toimpede the passage of heat from the cylinder head A to the spark plug D,as shown in Figure l, or the spark plug E, as shown in Figure 4. .Thecooling fins B will assist in cooling the head A, while the spark plug Dwill be cooled by the air-stream passing thereover. Since the heat inthe cylinder head A cannot readily be transmitted to the plug D, theplug D will not become overheated in use.

The bushing 5 is provided with a screw-threaded bore 8 to receive astandard size spark plug. The bore 8 also may be made oi any desireddiameter to accommodate the particular size of spark plug. Acircumierential shoulder 9 is formed on the cup I at a point below thetop thereof, thereby leaving a circular flange ill at the top of the cupI. The upper part of the shoulder 9 forms a seat II to receive a caphereinafter described. The shoulder 9 is provided with the plurality ofopenings l2 to receive a cap-holding means hereinatter described.

As shown by Figure 1, the extension or cup 1 does not extend to the topof the spark plug D, but terminates at a point below the exposedterminal or the plug D. The plug D is shown as provided with theordinary connecting means in common use where no radio shielding isemployed. Of course, any other form of plug D may be used. When usedwithout any radio shielding the construction heretofore described willact merely as a spark plug bushing. However, since the top edge III ofthe cup I is sumciently far removed from the terminal of the spark plugD, there can be no flash-overs from the terminal to the cup. There is noresulting disadvantage from using the cup 1 without a radio shield incombination therewith. When it is desired to use a radio shield for thespark plug it is not necessary to remove the bushing 5 or the cup 1 orto employ a dlfierent size spark plug. A shielding cap may be applieddirectly to the cup 1 of the bushing 5 at any time without the necessityof removing the bushing 5.

In Figures 2 and 4 is illustrated a cap for use with the bushing. Ametallic shell I! is provided with a recess ll on its lower edge. Theshell I3 is adapted to seat on the upper side oi the shoulder 9, asindicated at ll, while the flange l0 enters the recess It. A washer I5is disposed in the recess so that a fluid-tight seal is provided betweenthe shell I! and the cup 'I. At the same time an electrical contact ismade between the seat II and the shell la.

The shell I3 is provided with an outlet l6 and a lining of di-electricmaterial I]. The shielding cap which comprises the shell I! and theinsulation I! may be made as shown in my co-pending application -Ser.No. 657,166. The shell l3 also may be cast and the insulation i1 formedtherein.

In the outlet 16 is inserted a radio shielded conductor which may be asshown in my copending applications Ser. Nos. 657,166 and 657,167, whichcomprises a conductor i8 having insulation l9. Around the conductor I8is disposed a conduit formed of an inner sleeve 20 having anintermediate covering of wire 2| and a second protective covering ofwire 22. A flanged ferrule 23 is disposed on the end of the conduit andbears against a collar nut 24 securedto the outlet A conical washer, 25is disposed in the outlet to insure a fluid-tight connection and at thesame time a continuous electrical conductor is formed from the cup 1through the shell l3, the nut 24, the ferrule 23, and the conduit formedby the layers 22, 2|, and 20. By reason thereof, any electricalemanations improperly released from the spark plug will be absorbed andgrounded so that no interference with radio equipment will be possible.

A pointed screw 26 is disposed in the upper portion of the insulation l1within the shell l3 and is adapted to pierce the insulation 7 ll to makecontact with the conductor ll. A spring contact 21 issecured to thelower end of the screw 28 and is adapted to make contact with theterminal end of a spark plug E. It will be understood that various typesof spark plugs may be used and in this event various types or contacts21 may be used. However, it is common practice to use spark plugs of thetype designated by D where no shielding is used, and spark plugs of thetype designated by E where a radio shield is used.

A spring bail 28 has its lower ends engaged in the openings i2 and isprovided with a rotatable ball 29 on its upper end. Since the openings12 are in the shoulder 9 0! the cup I, and are securely fixed in bIace,the shell i3 will be se curely held on the cup 1. Since the bushing I isscrewed into-the cylinder head A, the shell 12 will not always be placedon the cup I in the same relative position. Therefore, a plurality ofopenings l2 are provided so that the bail 2| may be selectively disposedin any of several openings l2.

From the foregoing it will be seen that a complete radio shield isprovided for the spark plug by using the extension 1 of the bushing i asthe lower portion of the shield. At the same time, if it is desired touse the spark plug without a radio shield, the ball 28 is swung from thetop of the shell I3 and its lower ends removed from the openings l2. Theshell l3 thus can be removed and the conductor ll con nected to thespark plug D or E in the ordinary way. When used without the shieldspark plug failure cannot be caused by flash-overs from the spark plugterminal to the cup I by reason of the fact that the top of the cup I isso tar removed from the spark plug terminal.

Having thus fully described the invention, what is claimed as new anddesired to be secured by Letters Patent is:

1. In combination with a spark plug and a cable therefor, a spark plugshield comprising a bushing disposed in the cylinder head around thespark plug and formed with an extension projecting above the surface ofthe cylinder head and surrounding the base 01' the spark plug and a capdisposed over the upper part of the plug and in electrical contact withthe extension on the bushing.

2. In combination with a spark plug and a cable therefor, a'spark plugshield comprising a bushing disposed in the cylinder head around thespark plug and formed with an extension projecting above the surface ofthe cylinder head and surrounding the base of the spark plug, saidextension terminating sumciently far below the terminal of the sparkplug to prevent flashes from the terminal to the extension, and a capdisposed over the upper part ot the plug and in electrical contact withthe extension on the bushing.

3. In combination with a spark plug and a cable therefor, a spark plugshield comprising a bushing disposed in the cylinder head around thespark plug and formed with any-"extension projecting above the surfaceof the cylinder head and surrounding the base of the spark plug, saidextension being formed with;; seat toreceive a cap, and a cap disposedove't-gthe upper part of the plug and seated on we extension; electricalcontact with the extension on the bushing.

and in 4. In combinat on with a spark plug and a -means to maintain thecap on the bushing.

5. In combination with aspark plug and a cable therefor, a spark plugshield comprising a bushing disposed in the cylinder head around thespark plug and formed with an extension projecting above the surface ofthe cylinder head and surrounding the base of the spark plug, saidextension being formed with a seat to receive a cap, a cap disposed overthe upper part of the plug andseated on the extension, and a bailtomaintain the cap on the bushing.

6. A spark plug bushing adapted to be dw posed in a cylinder head tosurround the base of a spark plug, said bushing being formed with anintegral extension projecting above the surface of the cylinder head andsurrounding the lower part of a spark plug, and said extension havingformed on the upper edge thereof an annular flange to provide a seat andhaving openings formed. therein to receive cap retaining 7. Incombination with a spark plug and a cable therefor, a spark plug shieldcomprising a bushing disposed in the cylinder head around the spark plugand formed with an extension projecting above the surface of thecylinder head and surrounding the base of the spark plug, said bushingbeing adapted for use with or without a cap and said extensionterminating sufliciently' far below the terminal of the spark plug toprevent flashes from the terminal to the extension when used without acap, and a cap disposed over the upper part of the plug and inelectrical contact with the extension on the bushing.

8. In combination with a spark plug and a cable therefor, a spark plugshield comprising a bushing disposed in the cylinder head around thespark plug and formed with an extension projecting above the surface ofthe cylinder head and surrounding the base of the spark plug, saidextension terminating sumciently far below the terminal of the sparkplug to prevent flashes from'the terminal to the extension and saidextension beingformed with an irregular upper edge to provide a seat fora cap, and a cap disposed over the plug and in electrical contact withthe extension on the bushing.

JOSEPH J. MASCUCH.

